1. Field of the Invention
This invention relates to a surface shape measuring apparatus and method, and particularly to a surface shape measuring apparatus and method suitable for measuring the asymmetrical component of the surface shape of each surface of an optical system comprised of a single lens or a plurality of optical elements while the optical system remains incorporated in ironware.
2. Related Background Art
Recently, high-performance optical systems have come to be required in various optical systems. In a high-performance optical system, it is necessary to approximate residual aberration to zero to the utmost, and from the viewpoints of both of design and manufacture, it is necessary to make wavefront aberration remaining in the optical system small.
To make the wavefront aberration of the high-performance optical system have a good level, it is necessary to reduce the manufacturing errors of the surface accuracy, homogeneity, etc. of a single lens which is a constituent in the manufacture, and more approximate individual optical elements to design values. For this purpose, various measuring methods and working methods have heretofore been proposed and carried out.
However, even in a state in which the individual optical elements are approximate to the design values, there is a case where the high-performance optical system does not achieve desired performance in its assembled state, i.e., a state in which each lens element is in ironware.
It is conceivable that the desired performance cannot be achieved due to a lens holding method or lens strain by dust, injury or the like. When the strain is created in the inner part of the assembled optical system, it has been difficult to measure the amount of surface strain by a simple method.
The surface shape measuring apparatus and method of the present invention have been made in view of the situation in which the performance of an optical system could heretofore be evaluated only in a state in which an optical system to be measured was entirely assembled and the internal states of individual constituents could not be measured. Moreover, heretofore, the evaluation of the optical system to be measured could be done only by a wavefront transmitted through the entire optical system to be measured, and the internal states of the individual constituents could not be known.
The present invention has as an object thereof to measure the internal state of an optical system to be measured in its assembled state.
Other objects of the present invention will become apparent from the following description of some embodiments of the invention.